Paint strippers are important industrial chemicals and are used both in the finishing of manufactured articles and in the clean-up of painting facilities. Paint strippers are used in particularly large volumes in the automotive industry for cleaning paint spray booths and material handling equipment.
The threshold requirements for a good paint stripping composition are that it provides quick stripping action and that it does not harm the parts being stripped. It is also quite important that a paint stripping composition, particularly one used in large volumes by industry, be non-hazardous and of low toxicity to both animal and plant life so as to minimize any potential harm and costs associated with its disposal and handling. Toward that end, the stripper should be of fairly low volatility and flammability and preferably should be non-flammable. It is also desirable that the paint stripping composition be either soluble or dispersible in water so as to facilitate the rinsability of stripped parts. Finally, it is important that any stripping composition be of low cost and/or readily recoverable for reuse.
There are a large number of paint stripping compositions which are known in the prior art; however, the prior art is still deficient in providing the paint stripping compositions which meet foregoing criteria. Organic solvents such as benzene, toluene, cyclohexanone, methyl ethyl ketone and mineral spirits as well as halocarbons, such as methylene chloride, have long been used as paint strippers. While certain of such materials do have utility in particular applications, they are not generally applicable to large scale stripping operations because of environmental hazards, flammability and cost. Alkaline materials such as sodium or potassium hydroxide are low cost, effective paint strippers; however, they are inherently dangerous materials and calm damage a variety of substrates. Similar problems hold for acid based strippers. With the technological advent of current paint formulations such as the two (2) component urethanes, water-based base coats, and electrolytically deposited (E-coat) paints, the aforementioned stripper components are often useless.
In an effort to overcome the problems of such prior art stripping materials, industry has turned to blends of particular solvents. Pat. No. 4,120,810 discloses the use of N-methyl pyrrolidone together with a high molecular weight aromatic hydrocarbon for stripping paint. Pat. No. 4,732,695 discloses the use of N-methyl pyrrolidone together with benzyl alcohol and naphtha as a paint stripper. While both of these compositions do provide a material having somewhat lowered hazards, the compositions are fairly expensive and their stripping action is fairly slow.
There is clearly a need for a paint stripping composition which is non-hazardous, low cost and which provides for rapid and thorough stripping action. In accord with the principles of the present invention, it has been found that benzyl alcohol and water combine synergistically to provide a highly effective, low cost, low toxicity paint stripping composition. It is surprising and counter-intuitive that these two materials should cooperate in this manner since benzyl alcohol itself is only moderately effective as a paint stripper and water is a non-solvent for the paint compositions in question. It would thus be expected that the combination, at best, would be worse than benzyl alcohol in terms of stripping action. However, as will be detailed hereinbelow, it has been found that mixtures of benzyl alcohol and water provide a paint stripping composition which is far superior to prior art products and which is low in cost and toxicity. These and other advantages of the present invention will be readily apparent from the discussion, description and examples which follow.